Blend composition of sulfo EPDM&#39;s having improved tear properties

ABSTRACT

An elastomeric blend composition having improved tear properties and having a viscosity at 0.73 sec -1  and at 200° C. of about 8×10 3  to about 8×10 5  poises, said composition formable into an elastomeric article, which comprises: 
     (a) a neutralized sulfonated EPDM terpolymer having a viscosity at 0.73 sec -1  and at 200° C. of about 5×10 4  poises to about 5×10 6  poises and about 10 to about 50 meq. sulfonate groups per 100 grams of said sulfonated EPDM terpolymer, said sulfonate groups being neutralized; and 
     (b) about 2 to about 60 parts by weight of a fluorohydrocarbon elastomer per 100 parts of such sulfonated EPDM terpolymer.

FIELD OF THE INVENTION

This invention relates to extrusion and injection moldable typeelastomeric compositions having improved tear properties and having aviscosity at 200° C. at 0.73 sec⁻¹ of about 8×10³ to about 8×10⁶ poises.The compositions used for elastomeric articles include a major portionof neutralized sulfonated EPDM terpolymer and a minor portion of afluorohydrocarbon elastomer and optionally less than about 150 parts byweight of a non-polar process oil per 100 parts of the sulfonatedpolymer; less than about 300 parts by weight of a filler per 100 partsof the sulfonated polymer; and a preferential plasticizer at about 1 toabout 60 parts by weight per 100 parts of the sulfonated elastomericpolymer.

These blend compositions can be readily processed due to their superiorrheological properties on conventional plastic fabrication equipmentinto elastomeric articles having improved tear propertiescharacteristics.

BACKGROUND OF THE INVENTION

Recently, a new class of thermoelastic sulfonated polymers has beendescribed in a number of U.S. patents. These sulfonated polymers arederived from polymeric materials having olefinic unsaturation,especially elastomeric polymers such as Butyl and EPDM rubbers. U.S.Pat. No. 3,642,728, herein incorporated by reference, clearly teaches amethod of selective sulfonation of olefinic unsaturation sites of anelastomeric polymer to form an acid form of a sulfonated elastomericpolymer. The olefinic sites of the elastomeric polymer are sulfonated bymeans of a complex of a sulfur trioxide donor and a Lewis base. The SO₃H groups of the sulfonated elastomer can be readily neutralized with abasic material to form an ionically cross-linked elastomer havingsubstantially improved physical properties over an unsulfonatedelastomer at room temperature. However, these ionically cross-linkedelastomers, may be processed like a conventional thermoplastic atelevated temperatures under a shear force in the presence of selectedpreferential plasticizers which dissipate the ionic associations at theelevated temperatures thereby creating a reprocessable elastomer.

The basic materials used as neutralizing agents are selected fromorganic amines or basic materials selected from Groups I, II, III, IV,V, VI-B, VII-B and VIII and mixtures thereof of the Periodic Table ofElements. Although these sulfonated elastomeric polymers prepared by theprocess of this patent are readily useable in a certain number oflimited applications, they are not as readily adaptable for themanufacture of an extrudable and injection moldable elastomeric articleas are the improved compositions of the present invention, wherein bothimproved tear and rheological properties are realized.

U.S. Pat. No. 3,836,511, herein incorporated by reference, teaches animproved process for the sulfonation of the olefinic sites of theelastomeric polymer, wherein the improved sulfonating agent is selectedfrom acetyl sulfate, propionyl sulfate and butyryl sulfate. Theneutralizing agents employed to neutralize the acid form of thesulfonated elastomeric polymers are organic amines. The resultantionically cross-linked sulfonated elastomers prepared by this process donot exhibit both the improved tear and rheological properties of thecompositions of the present invention.

U.S. Pat. No. 3,870,841, herein incorporated by reference, teaches amethod of plasticization of the polymeric backbone of a neutralizedsulfonated plastic polymer by means of a polymer chain plasticizer whichis a liquid compound having a boiling point of at least about 120° F.The polymer chain plasticizer is selected from a dialkyl phthalate, aprocess oil or an organic acid ester. Additionally, a domain plasticizercan be incorporated into the composition, wherein the domain plasticizerreversibly disrupts the association of the sulfonated groups at thetemperature of forming. The compositions formed by this process are notsuitable for the manufacture of high performance elastomeric articlesformed by extrusion or injection molding process as are the compositionsof the present invention.

U.S. Pat. No. 3,847,854, herein incorporated by reference, teaches amethod of improving the processability of neutralized sulfonatedelastomeric polymers by the addition of a preferential plasticizer whichhas at least one functional constituent which exhibits a bond momentwhose absolute value is at least 0.6 Debyes, and must be a liquid at thedesired processing temperature of the neutralized sulfonated elastomericpolymer. Again, the compositions of the present invention are moreadaptable for use in the manufacture of high performance elastomericarticles.

Products resulting from the aforementioned methods for obtainingneutralized sulfonated elastomeric compositions, possess eitherunsuitable rheological properties or inferior tear properties for theapplications envisioned in the present invention.

For example, the physical properties of the resultant sulfonatedelastomeric products of these aforementioned patents are unsuitable formajor applications of automobile bumper parts, gaskets, weatherstripping and various appliance parts.

U.S. Pat. Nos. 3,974,240 and 3,974,241 of the present inventors, filedon Nov. 18, 1974, describe the blending of a crystalline polyolefinicmaterial with a neutralized sulfonated elastomeric polymer in an attemptto improve both the rheological and physical properties of theelastomeric polymer. The selection of the use of the crystallinepolyolefinic material to improve both the stiffness as well as improvingthe melt viscosity of the composition was based in part upon thelimitation of the use of fillers such as carbon black, clays, calciumcarbonate or silicates as a single additive to the elastomeric polymer.Although fillers in combination with an elastomeric polymer increase thehardness of the composition, these fillers deteriorate the meltviscosity of the resultant composition. These materials are moreadaptable for stiff elastomeric articles such as rubberized chair tipsor wheels whereas the compositions of the present invention are moreadapted for flexible elastomeric articles such as gaskets.

U.S. Pat. Nos. 4,220,573; 4,313,867; 4,118,360; 4,118,353; 4,166,751;4,134,870; 4,151,137; 4,157,992; and 4,169,820 all teach the concept ofusing sulfonated polymers for the formation of elastomeric articles;however, none of these U.S. Patents teach compositions with the improvedtear properties as exhibited by the compositions of the instantinvention.

The present invention teaches that sulfonated EPDM samples varying inthe type of cation when blended with fluorohydrocarbon elastomers yieldcompositions which have significantly improved tear properties, ascompared to a sulfonated EPDM terpolymer, which has poor tearproperties. A sulfonated EPDM terpolymer article that is cut or nickedwill readily tear.

The unique and novel improved compositions of the present inventionovercome the deficiencies of the aforementioned U.S. patents andapplications from both a rheological and tear properties aspect. Theblend compositions of the present invention solve the problem of havinga material which has both desirable tear and compression set propertiesfor the manufacture of an elastomeric article such as a gasket whereinthe extrudate of the resultant compositions do not exhibit melt fractureduring extrusion processing as is the case in some of the aforementionedpatents.

SUMMARY OF THE INVENTION

It has been found surprisingly that compositions formed from blends of amajor portion of a neutralized sulfonated EPDM terpolymer and a minorportion of a fluorohydrocarbon elastomer and optionally, fillers,non-polar backbone oils and a preferential plasticizer have suitablerheological and tear properties for the formation of an elastomericarticle, such as gaskets, by an extrusion or injection molding process.

Accordingly, it is an object of our present invention to provide uniqueand novel compositions of matter for producing a high performanceelastomeric article having improved tear properties by an extrusion orinjection molding process, wherein the compositions of the elastomericarticles have a viscosity at 0.73 sec⁻¹ at 200° C./ of about 8×10³ toabout 8×10⁶ poises, and a Shore A Hardness of about 40 to about 85.

It is the object of the instant invention to describe a class ofcompounds based on sulfonated ethylene-propylene terpolymers which canbe processed on plastics type extrusion or injection molding equipmentat high rates and which possess improved tear characteristics. One ofthe essential aspects of the present invention comprises the discoverythat only a restricted class of the subject sulfonated elastomers may bereadily employed for extrusion or injection molding fabrication. Therestrictions are primarily associated with processing and productperformance characteristics. These characteristics are to a degreemodulated by the type and concentration of various compoundingingredients. The compositions of the instant invention will, therefore,involve a class of compositions based on a restrictive class ofsulfonated elastomers.

A substantial segment of the plastics and rubber fabrication industryemploys fabrication techniques known as extrusion or injection moldingto form articles which can be classified as sheet, profiles, tubing,film, and molded goods. The applications employing these fabricationtechniques such as automobile bumper parts, weather stripping,refrigerator door seals, and gaskets, etc. require materials which areflexible and tough. Two broad classifications of materials which havebeen used are vulcanized elastomers and plasticized thermoplastics suchas polyvinyl chloride (PVC). The fabrication of articles based onvulcanized elastomers is a major item of cost involving thevulcanization procedure. Not only is this step costly from an energyintensive viewpoint, but it is time consuming. The use of plasticatingextrusion and injection molding for thermoplastic materials is moreeconomical and results in high extrusion rates for materials such asplasticized PVC. While these materials possess a degree of flexibility,they do not have a good rubbery feel or good low temperatureflexibility. It is therefore desirable to have materials which can beprocessed on plastics type processing equipment at conventional plasticsrates and which possess the flexibility and subjective rubberycharacteristics of vulcanized elastomers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a graph of stress versus elongation for some typicalblend compositions of the instant invention.

GENERAL DESCRIPTION

This present invention relates to unique and novel blend compositionshaving improved tear properties of a major portion neutralizedsulfonated EPDM terpolymer and a minor portion of a fluorohydrocarbonelastomer and optionally, a filler, and a non-polar process oil, whereinthe resultant composition has a viscosity at 0.73 sec⁻¹ at 200° C. ofabout 8×10³ to about 8×10⁶ poise, wherein the compositions are readilyprocessable in a conventional extrusion or injection molding processinto a high performance elastomeric article such as gaskets.

Various critically selected additives can be incorporated into the blendcompositions such as a polyolefin thermoplastic for further modificationof hardness as well as rheological properties, a pigment, an external,internal lubricant for improvement of the physical appearance such asshine of the finished article as well as the ability to easily processthe composition during extrusion, and a reinforcing filler such assilica or carbon black, wherein the reinforcing filler constitutes aminor portion of the composition.

The neutralized sulfonated elastomeric polymers of this present instantinvention are EPDM terpolymers.

The EPDM terpolymers which are used in the blend compositions as theunsulfonated species are similar or identical to those used to form thesulfonated EPDM terpolymers and are low unsaturated polymers havingabout 1 to about 10.0 wt % olefinic unsaturation, more preferably about2 to about 8, most preferably about 3 to 7 defined according to thedefinition as found in ASTM-D-1418-64 and is intended to meanterpolymers containing ethylene and propylene in the backbone and adiene which introduces unsaturation in the side group. Illustrativemethods for producing these terpolymers are found in U.S. Pat. No.3,280,082, British Pat. No. 1,030,289 and French Pat. No. 1,386,600,which are incorporated herein by reference. The preferred polymerscontain about 25 to about 75 wt % ethylene and about 1 to about 10 wt %of a diene monomer, the balance of the polymer being propylene.Preferably, the polymer contains about 30 to about 70 wt % ethylene,e.g. 50 wt % and about 2.6 to about 8.0 wt % diene monomer, e.g. 5.0 wt%. The diene monomer is preferably a non-conjugated diene.

Illustrative of these non-conjugated diene monomers which may be used inthe terpolymer (EPDM) are 1, 4-hexadiene, dicyclopentadiene,5-ethylidene-2-norborene, 5-methylene-2-norbornene,5-propenyl-2-norborene, and methyl tetrahydroindene.

A typical EPDM is Vistalon 2504 (Exxon Chemical Co.), a terpolymerhaving a Mooney viscosity (ML, 1+8, 212° F.) of about 40 and having anethylene content of about 50 wt % and a 5-ethylidene-2-norbornenecontent of about 5.0 wt %. The Mn of Vistalon 2504 is about 47,000, theMv is about 145,000 and the Mw is about 174,000.

Another EPDM terpolymer Vistalon 2504-20 is derived from Vistalon 2504(Exxon Chemical Co.) by a controlled extrusion process, wherein theresultant Mooney viscosity at 212° F. is about 20. The Mn of Vistalon2504-20 is about 26,000, the Mv is about 90,000 and the Mw is about125,000.

Nordel 1320 (DuPont) is another terpolymer having a Mooney viscosity at212° F. of about 25 and having about 53 wt % of ethylene, about 3.5 wt %of 1,4-hexadiene, and about 43.5 wt % of propylene.

The EPDM terpolymers of this invention have a number average molecularweight (Mn) of about 10,000 to about 200,000, more preferably of about15,000 to about 100,000, most preferably of about 20,000 to about60,000. The Mooney viscosity (ML, 1+8, 212° F.) of the EPDM terpolymeris about 5 to about 60, more preferably about 10 to about 50, mostpreferbly about 15 to about 40. The Mv of the EPDM terpolymer ispreferably below about 350,000 and more preferably below about 300,000.The Mw of the EPDM terpolymer is preferably below about 500,000 and morepreferably below about 350,000.

The EP copolymer of the instant invention have a molecular weight Mn ofabout 10,000 to about 200,000, and more preferably about 15,000 to about100,000 and the copolymer has about 40 to about 75 weight percentethylene therein.

In carrying out the sulfonation of the EPDM terpolymer of the instantinvention, the EPDM terpolymer is dissolved in a non-reactive solventsuch as a chlorinated aliphatic solvent, chlorinated aromatichydrocarbon, an aromatic hydrocarbon, or an aliphatic hydrocarbon suchas carbon tetrachloride, dichloroethane, chlorobenzene, benzene,toluene, xylene, cyclohexane, pentane, isopentane, hexane, isohexane orheptane. The preferred solvents are the lower boiling aliphatichydrocarbons. A sulfonating agent is added to the solution of the EPDMterpolymer and non-reactive solvent at a temperature of about -100° C.to about 100° C. for a period of time of about 1 to about 60 minutes,most preferably at room temperature for about 5 to about 45 minutes; andmost preferably about 15 to about 30. Typical sulfonating agents aredescribed in U.S. Pat. Nos. 3,642,728 and 3,836,511, previouslyincorporated herein by reference. These sulfonating agents are selectedfrom an acyl sulfate, a mixture of sulfuric acid and an acid anhydrideor a complex of a sulfur trioxide donor and a Lewis base containingoxygen, sulfur, or phosphorous. Typical sulfur trioxide donors are SO₃,chlorosulfonic acid, fluorosulfonic acid, sulfuric acid, oleum, etc.Typical Lewis bases are: dioxane, tetrahydrofuran, tetrahydrothiopheneor triethyl phosphate. The most preferred sulfonation agent for thisinvention is an acyl sulfate selected from the group consistingessentially of benzoyl, acetyl, propionyl or butyryl sulfate. The acylsulfate can be formed in situ in the reaction medium or pregeneratedbefore its addition to the reaction medium in a chlorinated aliphatic oraromatic hydrocarbon.

It should be pointed out that neither the sulfonating agent nor themanner of sulfonation is critical, provided that the sulfonating methoddoes not degrade the polymeric backbone of the EPDM terpolymer. Thereaction is quenched with an aliphatic alcohol such as methanol, ethanolor isopropanol, with an aromatic hydroxyl compound, such as phenol, acycloaliphatic alcohol such as cyclohexanol or with water. Theunneutralized sulfonated EPDM terpolymer has about 10 to about 100 meqsulfonated groups per 100 grams of sulfonated polymer, more preferablyabout 15 to about 50; and most preferably about 20 to about 40. The meqof sulfonate groups per 100 grams of polymer is determined by bothtitration of the polymeric sulfonic acid and Dietert Sulfur analysis. Inthe titration of the sulfonic acid, the polymer is dissolved in solventconsisting of 95 parts of toluene and 5 parts of methanol at aconcentration level of 50 grams per liter of solvent. The unneutralizedform is titrated with ethanolic sodium hydroxide to anAlizarin-Thymolphthalein end-point.

The unneutralized sulfonated EPDM terpolymer is gel free andhydrolytically stable. Gel is measured by stirring a given weight ofpolymer in a solvent comprised of 95 toluene-5-methanol at aconcentration of 5 wt %, for 24 hours, allowing the mixture to settle,withdrawing a weighted sample of the supernatant solution andevaporating to dryness.

Hydrolytically stable means that the acid function, in this case thesulfonic acid, will not be eliminated under neutral or slightly basicconditions to a neutral moiety which is incapable of being converted tohighly ionic functionality.

Neutralization of the unneutralized sulfonated EPDM terpolymer is doneby the addition of a solution of a basic salt to the acid form of thesulfonated elastomeric polymer dissolved in the mixture of the aliphaticalcohol and non-reactive solvent. The basic salt is dissolved in abinary solvent system consisting of water and/or an aliphatic alcohol.The counterion of the basic salt is selected from the group consistingof antimony, iron, aluminum, lead, and Groups I-A, II-A, I-B and II-B ofthe Periodic Table of Elements and mixtures thereof. The anion of thebasic salt is selected from the group consisting of a carboxylic acidhaving from about 1 to about 4 carbon atoms, a hydroxide, or alkoxideand mixtures thereof. The preferred neutralizing agent is a metalacetate, more preferably zinc acetate. Sufficient metal salt of thecarboxylic acid is added to the solution of the unneutralized sulfonatedEPDM terpolymer to effect neutralization. It is preferable to neutralizeat least 95% of the sulfonate groups, more preferably about 98%, mostpreferably 100%.

Examples of metal oxides useful in preparing metal sulfonates are MgO,CaO, BaO, ZnO, Ag₂ O, PbO₂ and Pb₃ O₄. Useful examples of metalhydroxides are NaOH, KOH, LiOH, Mg(OH)₂ and Ba(OH)₂. The resultantneutralized sulfonated EPDM terpolymer has a viscosity at 0.73 sec⁻¹ at200° C. of about 3×10⁵ poises to about 5×10⁸ poises, more preferably ofabout 5×10⁵ poises to about 5×10⁶ poises and most preferably about 5×10⁵poises to about 3.5×10⁶ poises.

A means of characterizing the apparent molecular weight of a polymerinvolves the use of melt rheological measurements. For ionic polymers,this is the preferred method since solution techniques are difficult tointerpret due to the complex nature of the ionic association. Meltrheological measurements of apparent viscosity at a controlledtemperature and shear rate can be used as a measure of apparentmolecular weight of an ionic polymer. Although the exact relationshipbetween melt viscosity and apparent molecular weight for these ionicsystems is not known, for the purposes of this invention therelationship will be assumed to be one of direct proportionality. Thus,in comparing two materials, the one with the higher melt viscosity willbe associated with the higher apparent molecular weight.

The melt viscosity of the systems investigated were determined by theuse of an Instron Capillary Rheometer. Generally, the melt viscositymeasurements were made at a temperature of 200° C. and at various shearrates corresponding to crosshead speeds from 0.005 in/min to 20 in/min.The apparent viscosity at 200° C. and at a shear rate of 0.73 sec⁻¹(0.005 in/min) is employed as a characterization parameter in thisinvention. A measure of the melt elasticity of a given system can alsobe obtained from these rheological measurements. A type of flowinstability known as melt fracture is exhibited by many polymericmaterials of high molecular weight. This phenomenon is shear sensitiveand thus will generally exhibit itself at a given shear rate andtemperature. The shear rate for the onset of melt fracture indicates theupper shear rate for processing a given material. This is used as acharacterization parameter for compounds employed in extrusionprocessing.

The metal neutralized sulfonated EPDM terpolymers at the highersulfonate levels possess extremely high melt viscosities and are therebydifficult to process. The addition of ionic group plasticizers markedlyreduces melt viscosity and frequently enhances physical properties.

To the neutralized sulfonated EPDM terpolymer is added, in eithersolution or to the crumb form of the sulfonated elastomeric polymer, apreferential plasticizer selected from the group consisting ofcarboxylic acids having about 5 to about 30 carbon atoms, morepreferably about 8 to about 22 carbon atoms, and basic salts of thesecarboxylic acids, wherein the metal ion of the basic salt is selectedfrom the group consisting of aluminum, ammonium, lead and Groups I-A,II-A, I-B and II-B of the Periodic Table of Elements and mixturesthereof. The carboxylic acids are selected from the group consistingessentially of lauric, myristic, palmitic or stearic acids and mixturesthereof; e.g. zinc stearate, magnesium stearate, or zinc laurate.

The preferential plasticizer is incorporated into the neutralizedsulfonated elastomeric polymer at about 1 to about 60 parts by weightper 100 parts of the neutralized sulfonated EPDM terpolymer morepreferably at about 5 to about 40, and most preferably at about 7 toabout 25. The metallic salt of the fatty acid can also be used asneutralizing agent. In the case of the neutralizing agent andplasticizer being the identical chemical species, additional metallicsalt is added over the required levels of neutralization. Alternatively,other preferential plasticizers are selected from organic esters,phenols, trialkyl phosphates, alcohols, amines, amides, ammonium andamine salts of carboxylic acids and mixtures thereof. The preferredplasticizers are selected from the group consisting of fatty acid andmetallic salts of fatty acid and mixtures thereof. The resultantneutralized sulfonated EPDM terpolymer with preferential plasticizer isisolated from the solution by conventional steam stripping andfiltration.

The resultant neutralized and plasticized sulfonated EPDM terpolymer hasa viscosity at 200° C. and a shear rate of 0.73 sec⁻¹ of about 5×10⁴poise to about 5×10⁶ poise, more preferably of about 1×10⁵ poise toabout 1×10⁶ poise and most preferably of about 2×10⁵ poise to about1×10⁶ poise.

The neutralized sulfonated EPDM terpolymer is blended with afluorohydrocarbon elastomer and optionally a filler and a non-polarbackbone process oil by techniques well known in the art. For example,the blend composition can be compounded on a two-roll mill. Othermethods known in the art which are suitable for making thesecompositions include those methods employed in the plastic and elastomerindustries for mixing polymer systems. An excellent polymer blendcomposition of this invention can be obtained through the use of a highshear batch intensive mixer called the Banbury. Alternatively, economicadvantages in terms of time and labor savings can be obtained throughthe use of a Farrel Continuous Mixer, a twin screw extruder, or tandemextrusion techniques which are continuous mixing types of equipment. TheBanbury mixing device is the preferred batch type mixer, and the twinscrew extruder is the preferred continuous mixer.

The amount of the fluorohydrocarbon elastomer in the blend compositioncomprises about 2 to about 60 parts by weight per 100 parts of the metalneutralized sulfonated EPDM terpolymer, more preferably about 3 to about50 and most preferably about 4 to about 40.

The fluorohydrocarbon elastomers used in the present invention werechosen from a family of fluoropolymers which are manufactured by DuPont.These fluorohydrocarbon polymers are sold under the DuPont trademark,Viton®. Viton® polymers, generally speaking, are copolymers ofvinylidene fluoride and hexafluoropropylene, having the followingchemical structure: ##STR1## Similar types of fluorocarbon polymers arealso commercially manufactured by the 3M Company and are sold undertheir trademark Fluorel®. A variety of fluorocarbon polymers, varyingboth in the molecular weight and respective ratio of copolymer contentsare available. The commercial success of both such polymers, Viton® andFluorel®, stems from their exceptional thermal, chemical and oxidativeproperties. The fluorocarbon elastomers can readily be crosslinked viaradiation, peroxides and amine curative agents. The resulting productsare excellent for various military and industrial applications. Anymember of such fluorocarbon polymers could be used in the presentinvention, which have the desired range of molecular weight andcopolymer composition. Typically, the useful compositions involve theuse of vinylidene fluoride-hexafluoropropylene copolymers whosemolecular weight ranges from about 20,000 to 500,000, having Mooneyviscosity range from 45-65. The shore hardness of such copolymerstypically ranges from about 50 to about 100.

The fillers which can be optionally employed in the present inventionare selected from the group consisting of carbon blacks, talcs, groundcalcium carbonate, water precipitated calcium carbonate, anddelaminated, calcined and hydrated clays and mixtures thereof. Thesefillers are incorporated into the blend composition at less than about300 parts by weight per 100 parts of the neutralized sulfonated EPDMterpolymer, more preferably at less than about 250; and most preferablyat less than about 200. Typically, these fillers have a particle size ofabout 0.0 to about 20 microns, more preferably less than about 15, andmost preferably less than about 10. The oil absorption as measured bygrams of oil absorbed by 100 grams of the inorganic filler is about 10to about 100, more preferably about 10 to about 85 and most preferablyabout 10 to about 75. Typical inorganic fillers employed in thisinvention are illustrated in Table I. Reinforcing fillers such as carbonblacks typically have sizes below 0.1 microns and oil absorption aboveabout 100. These reinforcing fillers are optionally incorporated aloneor in addition to non-reinforcing fillers at a ratio of less than 1 partof reinforcing filler to 1 part of non-reinforcing filler, morepreferably less than about 0.5 and most preferably less than about 0.3.

                                      TABLE I                                     __________________________________________________________________________                         Oil Absorption                                                                grams of oil/                                                                          Specific                                                                           Avg. Particle                              Filler       Code #  100 grams of filler                                                                    gravity                                                                            Size Micron                                                                          pH                                  __________________________________________________________________________    calcium carbonate ground                                                                   Atomite 15       2.71        9.3                                 calcium carbonate                                                                          Purecal U                                                                             35       2.65 .03-.04                                                                              9.3                                 precipitated                                                                  delaminated clay                                                                           Polyfil DL                                                                            30       2.61   4.5  6.5-7.5                             hydrated clay                                                                              Suprex           2.6  2      4.0                                 calcined clay                                                                              Icecap K                                                                              50-55    2.63 1      5.0-6.0                             talc                                                                          magnesium silicate                                                                         Mistron Vapor                                                                         60-70    2.75 2      9.0-7.5                             alumino silicate                                                              __________________________________________________________________________

The oils which can be optionally employed in the present invention arenon-polar process oils having less than about 2 wt % polar typecompounds as measured by molecular type clay gel analysis. These oilsare selected from paraffinics ASTM Type 104B as defined inASTM-D-2226-70, aromatics ASTM Type 102 or naphthenics ASTM Type 104A,wherein the oil has a flash point by the Cleveland open cup of at least350° F., a pour point of less than 40° F., a viscosity of about 70 toabout 3000 s.s.u.'s at 100° F. and a number average molecular weight ofabout 300 to about 1000, and more preferably about 300 to 750. Thepreferred process oils are paraffinics. Table II illustrates typicaloils encompassed by the scope of this invention.

The oils are optionally incorporated into the blend composition at aconcentration level of less than about 150 parts by weight per 100 partsof the neutralized sulfonated EPDM terpolymer; more preferably at about5 to about 150, and most preferably at about 10 to about 150.

                  TABLE II                                                        ______________________________________                                                           Vis-               %     %                                                    cosity       %     Aro-  Satu-                             Type Oil                                                                              Oil Code # ssu     M.sub.n                                                                            Polars                                                                              matic rates                             ______________________________________                                        Paraffinic                                                                            Sunpar 115 155     400  0.3   12.7  87.0                              Paraffinic                                                                            Sunpar 180 750     570  0.7   17.0  82.3                              Paraffinic                                                                            Sunpar 2280                                                                              2907    720  1.5   22.0  76.5                              Paraffinic                                                                            Tufflo 6056                                                                              495     --   0.0    0.9  99.1                              Aromatic                                                                              Flexon 340 120     --   1.3   70.3  28.4                              Naphthenic                                                                            Flexon 765 505     --   0.9   20.8  78.3                              Naphthenic                                                                            Tufflo 6054                                                                              580     --   0.0    8.0  92.0                              ______________________________________                                    

DETAILED DESCRIPTION OF THE INVENTION EXAMPLE 1 Preparation ofSulfo-EPDM Polymer

Five hundred grams of an EPDM terpolymer (MD-76-5) was dissolved underagitation in 5,000 ml of n-hexane at about 40° C. After all this polymerwas dissolved, the solution was cooled to low temperature and 25.83 mlof active anhydride (273.38 mmoles) was added. After that, whilestirring the mixture, 9.46 cc of 95% H₂ SO₄ (17.25 mmoles) was addeddrop-wise, the stirring of the solution was continued for an additional30 minutes for the sulfonation reaction to complete. After this periodthe sulfonation reaction was inactivated by adding 42.94 gm of zincacetate dissolved in 400/20 ml mixture of CH₃ OH/H₂ O. Antioxidant 2246(3.75 gm) was added to the cement and stirring was continued for anadditional 30 minutes. The resultant neutralized EPDM terpolymer wasisolated by steam stripping. It was then washed with distilled water andpulverized with water in a Waring blender, followed by filtering by arubber drum. The final drying of the polymer was done in an aromaticdryer at 100° C.

The sample is identified as zinc neutralized sulfonated EPDM terpolymer,TP-303.

The sulfur analyses of this sample was done by Dietert sulfur analysisand was found to have a group of 30 meq. per 100 g of sulfonatedpolymer.

EXAMPLE 2

In this example blend compositions of sulfonated EPDM and afluorohydrocarbon were made according to the ratio shown in Table III.

                  TABLE III                                                       ______________________________________                                        Blend #             1        2      3                                         ______________________________________                                        Sulfonated-EPDM (30 meq. Zn)                                                                      100      100    --                                        Fluorohydrocarbon Elastomer                                                                        40      --     100                                       (Viton ® E-45)*                                                           ______________________________________                                         *Viton ® is a DuPont trademark of a fluoroelastomer.                 

The samples were mill-mixed on a 3"×7" electrical mill at 380° F. from10 to 15 minutes until homogeneous blends were achieved. Samples werethen compression molded for tensile and tear propagation propertiesaccording to standard ASTM procedures.

(A) Tensile test pads=Molded 2"×2"×0.020" pads for 1-3 minutes at 350°F.

(B) Tear test samples=Molded 1"×4"×0.0035" specimens for 3" preheat, 3"full pressure (25 ton psi), 5" cooling under pressure at 350° F.

EXAMPLE 3

Specimens for tensile properties were tested following the standard ASTMtensile test method at 2" crosshead speed at room temperature.Similarly, the tear propagation properties were tested along the linesdescribed in ASTM D-1938-62T method. The ASTM D-1938-62T testessentially is the test to quantitatively measure the resistance to tearpropagation in the thin sheeting by a single tear method. This method oftest describes the procedure for determining the force in poundsnecessary to propagate a tear in thin sheeting (thickness of ˜0.04 in.)by a single tear method. The force in pounds to propagate a tear acrossa specimen was measured by employing a table model Instron 1122 using aconstant rate-of-grip separation and equipped for recording the loadcarried by the specimen and the amount of separation of the grips duringthe test. The separation was controlled at a rate of 10 inches perminute. Thickness of the specimens was measured by using a Starrettthickness gauge, model number 655-441. Not less than five specimens ofeach sample were tested.

Test specimens consisted of strips 3 inches long by 1 inch wide, with aclean longitudinal slit 2 inches long, cut using a sharp razor blade.

Test procedure was as follows: One side of the specimen was secured inone grip and the other side in the other grip of the constantrate-of-grip separation Instron tester, using an initial grip separationof 2 inches. The specimen was aligned so that its major axis coincidedwith an imaginary line joining the centers of the grips. A separationspeed of 10 inches per minute was used and the force was recorded on aload-time chart needed to propagate the tear through the entire un-slit1 inch portion. The resulting data are shown in Table IV.

                  TABLE IV                                                        ______________________________________                                        Blend #              1       2       3                                        ______________________________________                                        Tensile Strength*                                                             100% Modulus, psi    218     295     72                                       Tensile Strength, psi                                                                              373     1059    2                                        % Elongation         260     280     >1000                                    Tear Propagation                                                              Average Tear Propagation (lbs.)                                                                    33.6    15.3    35.2                                     Average Initial Tear Propagation                                                                   26.1    --      --                                       (lbs.)                                                                        Average Maximum Tear Propagation                                                                   33.6    --      --                                       (lbs)                                                                         (No. of Samples Tested)                                                                            9       8       7                                        (Standard Deviation) 8.2     0.5     1.2                                      (Average Sample Thickness, in.)                                                                    0.036   0.036   0.031                                    ______________________________________                                         *Method ASTM D935-B; room temperature, 22 hours.                         

It is clear from the above Table IV that sample 2 has significantlyinferior tear properties than the other two. Sample 1, which has about40 parts of a fluorohydrocarbon elastomer, has about a factor of 2higher tear resistance strength than sample 2, which is just asulfonated EPDM polymer by itself.

What is claimed is:
 1. An elastomeric blend composition having improvedtear properties and having a viscosity at 0.73 sec⁻¹ and at 200° C. ofabout 8×10³ to about 8×10⁶ poises, said composition formable into anelastomeric article, which comprises:(a) a neutralized sulfonated EPDMterpolymer having a viscosity at 0.73 sec⁻¹ and at 200° C. of about5×10⁴ poises to about 5×10⁶ poises and about 10 to about 50 meq.sulfonate groups per 100 grams of said sulfonated EPDM terpolymer, saidsulfonate groups being neutralized; and (b) about 2 to about 60 parts byweight of a fluorohydrocarbon elastomer per 100 parts of such sulfonatedEPDM terpolymer.
 2. A composition according to claim further includingabout 1 to about 60 parts by weight of a preferential plasticizer per100 parts of said sulfonated EPDM terpolymers.
 3. A compositionaccording to claims 1 or 2, wherein said sulfonated groups areneutralized with a counterion being selected from the group consistingof antimony, iron, aluminum, lead and Groups I-A, II-A, I-B and II-B ofthe Periodic Table of Elements and mixtures thereof.
 4. A compositionaccording to claim 1, wherein said EPDM terpolymer consists of about 40to about 75 wt % of ethylene, of about 10 to about 58 wt % of propyleneand of about 2 to about 10 wt % of a non-conjugated diene.
 5. Acomposition according to claim 4, wherein said non-conjugated diene isselected from the group consisting of 1,4-hexadiene, dicyclopentadiene,5-alkylidene-2-norbornenes, 5-alkenyl-2-norbornenes andtetrahydroindene.
 6. A composition according to claim 5, wherein saidnon-conjugated diene is 5-ethylidene-2-norbornene.
 7. A compositionaccording to claim 1 or 2, further including less than about 300 partsby weight of a filler per 100 parts of said sulfonated EPDM terpolymer.8. A composition according to claim 1 further including less than about150 parts by weight of a non-polar process oil per 100 parts of saidsulfonated EPDM terpolymer.
 9. A composition according to claim 2,wherein said preferential plasticizer has a melting point of at least25° C. and is selected from the group consisting of carboxylic acidshaving at least 8 carbon atoms, metallic salts of said carboxylic acids,phenols, phosphates, amides, ammonium and amine salts of said carboxylicacids, and amines and mixtures thereof.
 10. A composition according toclaims 2 or 9, wherein said preferential plasticizer is a combination ofa carboxylic acid and metallic salt of said carboxylic acid, a metal ionof said metallic salt being selected from the group consisting ofaluminum, antimony, iron, lead and Groups I-A, II-A, I-B, and II-B ofthe Periodic Table of Elements and mixtures thereof.
 11. A compositionaccording to claim 10, wherein said metallic salt is selected from thegroup consisting of zinc stearate or calcium stearate.
 12. A compositionaccording to claim 7, wherein said filler is selected from the groupconsisting of clay, talc and calcium carbonate, and mixtures thereof.13. A composition according to claim 8, wherein said non-polar processoil is selected from the group consisting of paraffinic, naphthenic andaromatics and mixtures thereof.